The present invention relates to improvements in a speed change unit for a tiller comprising two gears fixedly mounted on one shaft, a driven gear mounted on another shaft and always meshing with one of the gears, a slidable gear mounted on further shaft and selectively meshing with the other gear or the driven gear.
According to the arrangement, at least four gears are necessary to change the directions of rotation of the slidable gear which transmits a power to a transmission systems for axles of wheels. Further, it is needed that the slidable gear has a large width axially thereof for providing a neutral position. This causes a width of a transmission case wide and a number of parts including the four gears makes a cost of the tiller high. This invention intends to overcome these problems.